The part of the Constitution that by accident was not read in the House's Constitution-reading ritual. Somebody turned 2 pages at once. Intentionally left out was the Three-Fifths Clause. Obviously, the accidental omission was unfortunate, but was the intentional omission wise?
You can read some of the debate on that question at the link. I think it's quite interesting that we list the amendments after the original document instead of integrating them into a new, amended document. Considering how much shame we now feel for the parts about slavery and how much we want to revere the document, you might think we'd have changed our approach to formatting by now. But our traditionalism about the Constitution extends even to the placement of the amendments.